No messaging from Rogers at all. I just logged on my account today and it's showing 12GB.
With a share everything plan, the advertised price is what you pay for your first phone line. You can add additional lines to the account, for a fee. These additional lines then all get unlimited talk/text and share the pool of data that your Share everything plan already has. It starts at $35 if you bring your own phone, up to $55 if you want to get a subsidized smartphone like the iPhone6.